Process for the manufacture of threads, films, and the like from cellulose derivatives



Still A'tti tit:

Patented Aug. 7, 192 8.

UNITED STATES ERNST BERL, OF DARMSTADT, GERMANY.

PROCESS FOR THE MANUFACTURE OF THREADS, FILMS, AND THE LIKE FROM GELLULOSE DERIVATIVES.

No Drawing. Application filed March 11, 1925, Serial No. 14,788, and in Germany March 17, 1924.

thread are obtained whilst at the same time a stretching of the thread is impossible.

It has further been proposed to coagulate structure existing in a-more or less perfect.- ly dissolved or gelated state in an aqueous solution which contained a solvent. This process also yields only imperfect products with reference to the solidityof the struc ture obtained.

According to the invention in contradistinction to the above the cellulose derivative such as cellulose ester, cellulose ether or mixtures thereof are converted into solutions or gelations by means of organic solvents and the product obtained is treated in precipitating baths which contain solvents besides solutions of salts.

The quantity of solvent to be added to the salt-containing precipitating baths ispreferably adjusted according to the desired speed of precipitation. In carrying out the invention one can ad vanta'geously proceed so that the solidification of the structure is undertaken, in steps by treating in several consecutive precipitating baths which advantageously have diminishing contents of solvent and increasing salt solution content, as for instance by first using baths containing solvents in their dilute form and later using baths containing salt solutionsin concentrated form.

It is possible for example to proceed by initiating the precipitating process, after dissolving the materials in common solvents,

by passing the formed structure into a first bath, whichcontains the solvent or solvents in a' ratherdilute condition. By this means a sufficient solidification for the permanence 'ofform of the desired structure is produced. Tn order'now to impart to the structure produced the qualities of strength necessary for the further treatment, the structure is passed into a further bath which contains concentrated salt solution.

To the first bath, which contains the dilute solvents, constituents of the nature of the second bath, as for example a small quantity of fixing salt, may be added; or conversely, to the second bath may be added constituents of the nature of the first bath. By this means the result is obtained that the quantity of the solvent taken up by the gelations is gradually reduced and is withdrawn from the structure again before the final fixing.

The incompletely acting solvents that come into consideration according to the invention are, for example mixtures of aloehol and ether, or of acetone and water or the like, while for the coagulation and solidification of the produced structures more or less concentrated salt solutions may be employed for example solutions of nitrates, such as calcium nitrate or. ammonium nitrates, or else ammonium sulphate or other salt solutions.

The speed of the precipitation may be widely varied not only .by the already mentioned larger or smaller addition of solvent or gelatinizing media to the precipitating liquid, but also for example by altering the temperature. The threads, etc., may be spun by means of the invention, according to the stretch spinning process. In working the process the countercurrent principle may be'employed and temperature of the precipitating liquids may vary along the ixiprse its contact with the threads or the Examples: 1. A solution of nitro-eellulose in alcoholic ether is passed through fine nozzles directly into a'mixture of Water and alcohol containing about 60 per cent of methyl or ethyl alcohol. After the passing of this first precipitating bath the thread passes into a solution of common salt or sodium acetate or calcium nitrate. The thread produced is clear like glass, transparent, and of remarkably favourable mechanical properties as regards its strength and extensibility.

2. A mixture of acetyl cellulose and cellulose nitrate is allowed to flow through a slotshaped aperture into a mixed solution consistlng of acetone and carbon tetrachloride. After the passage of this mixture the spun material passes into a concentrated solution h water and then into a mixture or ammonium nitrate which tures from cellulose of ammonium nitrate as a second precipitating bath The coagulated structure. exhibits great strength and can be drawn out of the precipitating liquid Withremarkable speed.

3. A dilute solution of methyl cellulose and acetyl cellulose in methyl ethyl ketone isv first passed into a mixture of of calcium contains methyl ethyl ketone,'a'nd then into the pure salt solution free from ketone.

The still plastic thread formed in the first precipitating bath is extensible and can be drawn out into exceedingly fine threads, whichwundergo their complete coagulation by the nitrated solution free from solvents.

What I claim is 1. Process for the production of strucderivatives consisting in converting the cellulose derivatives into solutions or gelations by means of organic sol; vents and treating the thus obtained products in precipitating baths which contain solvents in addition to salt solutions.

2. Process-according to claim 1 consisting in solidifying the structure in steps in a plur'ality of consecutive baths.

3. Process according to claim 1 consisting in solidifying the structure in steps by treatment in several consecutive baths, the baths having decreasing contents of solvents and increasing contents of salt solution.

4. Process for the reduction of structures of cellulose derivatlves consistin in converting the cellulpse" derivatives into soluacetone and tions or gelations by means of organic solvents and treating the thus obtained products in precipitating baths which contain solvents in quantities chosen corresponding to the desired speed of precipitation in addition to the salt solutions.

5. Process according to claim 1 consisting in using solutions of easily soluble nitrates as precipitating baths.

rocess according to claim 1 consisting in using calcium nitrate solution as the salt solution.

7. Process for the production of structures from cellulose derivatives consisting in converting cellulose ester into solution or elation by means of organic solvent an in treating the so-obtained structure in precipitating baths which contain solvents in addition to salt solutions.

8. Process for the production of structures from cellulose derivatives consisting in converting mixtures of cellulose esters and cellulose ethers into solution or gelation by means of organic solvent and in treating the so-obtained structure in precipitating 'baths which contain solvents in addition to salt solutions.

9. Process for the preparation of bodies from acidyl celluloses by spinning solution thereof into salt solutions, consisting in adding to the salt solutions substances which are solvent agents for the acidyl celluloses.

In testimony whereof I ain'x my signature DR. ERNST BERL. 

